The Measurement of Meloxicam and Meloxicam Metabolites in Rat Plasma Using a High-Performance Liquid Chromatography-Ultraviolet Spectrophotometry Method.

A high-performance liquid chromatography-ultraviolet spectrophotometry (HPLC-UV) method for the determination of meloxicam (MEL) and meloxicam metabolites (5'-hydroxy meloxicam (5-HMEL) and 5'-carboxy meloxicam (5-CMEL)) has been developed. After extraction of MEL, 5-HMEL, and 5-CMEL from rat plasma using Oasis HLB cartridges, the extracts were separated with a Luna C18 (2) 100 A column (5 µm, 4.6×150 mm, Phenomenex) using a mobile phase of 50 mM phosphate buffer (pH 2.15, solvent A) and acetonitrile (solvent B) at a flow rate of 0.8 mL/min in a linear gradient. The detection wavelength was 360 nm, and the internal standard (IS) was piroxicam. Each calibration curve was linear in the range of 40 to 1000 ng/mL (r2>0.999). The extraction rates of MEL, 5-HMEL, and 5-CMEL were greater than 86.9%. The intra- and inter-day accuracies were in the range of 95.0 to 119.0%, and the precision was 0.2 to 17.0%. To the best of our knowledge, this is the first report of the quantitative and qualitative measurement of meloxicam and each metabolite using an HPLC-UV method.